Process for inhibiting corrosion of tin-plated steel aerosol cans

ABSTRACT

PROPELLANT COMPOSITION INHIBITED AGAINST CORROSION OF TIN-PLATED STEEL AEROSOL CANS CONTAINING WATER-BASED CONCETRATES, CONSISTIG ESSENTIALLY OF AT LEAST ONE LIQUEFIED STURATED HYDROCARBON HAVING 3 OR 4 CARBON ATOMS AND ABOUT 0.01 TO 2% BY WEIGHT BASED ON THE HYDROCARBON OF NITROMETHANE OR 2-NITROPROPANE.

United States ABSTRACT OF THE DISCLOSURE =Propellant compositions, inhibited against corrosion of tin-plated steel aerosol cans containing water-based concentrates, consisting essentially of at least one liquefied saturated hydrocarbon having 3 or 4 carbon atoms and about 0.01 to 2% by weight based on the hydrocarbon of nitromethane or Z-nitropropane.

This invention relates to inhibited hydrocarbon propellant compositions which are non-corrosive to tin-plated steel aerosol cans containing water-based concentrates.

Aerosol products such as room deodorants, insecticides and hair sprays, which are composed of active ingredients combined with anhydrous organic solvents, are known commercially. These anhydrous flammable concentrates are propelled using nonflammable liquefied fluorocarbons such as monofluorotrichloromethane and symmetrical dichlorodifiuoromethane. When used in tin-plated steel aerosol cans, such formulations have no corrosive effect on the aerosol cans.

A multitude of aerosol products which contain concentrades emulsified with water is now being marketed. Since these concentrates are non-flammable, they can be blended with propellants other than liquefied fiuorocarbons, particularly with liquefied saturated hydrocarbons. Use of the hydrocarbon propellants, however, has been found to cause tin-plated steel aerosol cans to corrode and rust. It has, therefore, been necessary to coat the tin plating with either a lacquer or plastic material. Even with such coating, however, corrosion and rusting still occur.

It is, therefore, an object of the present invention to provide saturated hydrocarbon propellants which are inhibited against corrosion of tin-plated steel aerosol cans containing water-based concentrates. Other objects and advantages of the present invention will be apparent from the following description.

In accordance with the present invention, propellant compositions, inhibited against corrosion of tin-plated steel aerosol cans containing water-based concentrates, consist essentially of at least one liquefied saturated hydrocarbon having 3 or 4 carbon atoms and about 0.01 to 2% by weight based on the hydrocarbon of nitromethane or Z-nitropropane.

The hydrocarbon propellants comprise one or more liquefied saturated hydrocarbons containing 3 or 4 carbon atoms, specifically propane, isobutane, normal butane and mixtures thereof. The hydrocarbons may be either synthetic or natural hydrocarbons. In the case of natural hydrocarbons, the corrosive action on tin-plated steel aerosol cans is more acute. The natural hydrocarbons are obtained by conventional distillation of liquefied natural gas or petroleum and may be employed in crude or purified state. Purification of the natural hydrocarbons is generally carried out by passing the hydrocarbon through activated carbon and molecular sieves. The synthetic hydrocarbons are produced by conventional hydrocracking or hydroforming procedures.

The inhibitors are employed in amount varying from about 0.01 to 2% by weight based on the hydrocarbon.

atent O 'ice Preferably the amount varies from about 0.05 to 0.08% by weight based on the hydrocarbon. Smaller amounts of inhibitor are ineffective while larger amounts produce no further advantage and tend to become uneconomical.

The water-based concentrates contain, in addition to water, conventional emulsifying agents and active ingredients. If desired, the concentrates may also contain conventional organic solvents.

The corrosive effect of uninhibited hydrocarbon propellants in water-based concentrates is manifested by detinning of the tin plating and rusting of the steel aerosol can. The theory on which corrosion of the tin-plated steel aerosol cans is inhibited by nitromethane and Z-nitropropane is not known. It is believed, however, that these inhibitors may negate the corrosive effect of dissolved oxygen in the water and propellant.

The nitromethane and 2-nitropropane inhibitors are soluble in the hydrocarbon propellants. As desired, the inhibitors can be added to the hydrocarbon or to aerosol formulation containing the hydrocarbon.

The fact that nitromethane and 2-nitropropane effectively inhibit the corrosion of tin-plated steel aerosol cans was completely unpredictable and unexpected. Thus, closely related nitroalkanes, such as nitroethane and l-nitropropane, fail to adequately prevent such corrosion. In addition, other known corrosion inhibitors, such as phenol, vinylidene chloride and epoxidized linseed oil, are also unsuitable.

Examples are given hereafter illustrating evaluation of the present inhibitors, including comparative testing. These tests were carried out for a period of several weeks at a temperature of 110 F. Such tests are standard in the aerosol industry for evaluating the effect on aerosol cans of various materials which might be used therein. In the comparative tests, detinning of the cans is inevitably followed by rusting of the steel substrate.

EXAMPLE 1 Hydrocarbon: Can corrosion Synthetic isobutane (control) Detinning. Natural isobutane (control) Do. Mixture of synthetic and natural iso- Do.

butane (control). Synthetic isobutane containing 0.05%

No detinning. by weight of nitromethane.

Natural isobutane containing 0.05% Do.

by weight of nitromethane.

Natural isobutane containing 0.05% Detinning.

by weight of Epoxol 9-5 (epoxidized linseed oil).

Natural isobutane containing 0.05% Do.

by weight of phenol.

EXAMPLE 2 In further tests, formulations comprising by weight of water and 20% by weight of natural isobutane were placed in tin-plated steel aerosol cans. Potential inhibitors were added to the formulations, and the cans were capped and stored for a period of three weeks at a temperature of 110 F. Upon inspection of the cans after this period, the following results were noted:

Hydrocarbon: Can corrosion Isobutane (control) Detinning.

Isobutane containing 0.05% by No detinning.

weight of nitromethane.

Isobutane containing 2% by Do.

weight of nitromethane.

Isobutane containing 0.01% by Detinning.

weight of nitroethane.

Isobutane containing 0.05% by Do.

weight of nitroethane.

Isobutane containing 0.1% by Do.

weight of nitroethane.

Isobutane containing 0.2% by Do.

weight of nitroethane. Isobutane containing 1% by weight of nitroethane.

Preliminary detinning.

weight of l-nitropropane.

Isobutane containing 1% by weight of l-nitropropane.

Isobutane containing 0.05% by weight of 2-nitropropane.

Isobutane containing 0.1% by weight of 2-nitropropane.

Isobutane containing 0.2% by weight of 2-nitropropane.

Isobutane containing 1% weight of 2-nitropropane.

Isobutane containing 0.01% by weight of vinylidene chloride.

Isobutane containing 0.05% by weight of vinylidene chloride.

Isobutane containing 0.2% by weight of vinylidene chloride.

Isobutane containing 1% by weight of vinylidene chloride.

Isobutane containing 2% by weight of vinylidene chloride.

EXAMPLE Preliminary detinning.

No detinning.

Detinning.

In still further tests, insecticidal formulations containing natural isobutane as propellant were placed in tin- Component: Weight Pyrethrins (20%) 1.00 Piperonyl butoxide 1.25

p,p'-Dichlorodiphenyltrichloroethane 2.00 Arlacel 186 (an emulsifier composed of monoand diglycerides of fatty acids) 0.75 Methylene chloride 10.00 Water 55.00 Isobutane 30.00

The cans were capped and stored for a period of three weeks at a temperature of -F. Upon inspection of the cans after this period, the can containing no inhibitor had detinned whereas the can containing the nitromethane inhibitor showed no detinning.

I claim:

1. A process of inhibiting corrosion of a tin-plated steel aerosol can containing a water-based concentrate and at least one liquefied saturated hydrocarbon having 3 or 4 carbon atoms as propellant which comprises adding to the can about 0.01 to 2% by weight based on the hydrocarbon of nitromethane or 2-nitropropane.

2. A process according to claim 1 in which the hydrocarbon is a natural hydrocarbon.

3. A process according to claim 2 in which the inhibitor is nitromethane.

4. A process according to claim 2 in which the inhibitor is 2-nitropropane.

5. A process according to claim 3 in which the amount of nitromethane is about 0.05 to 0.08% by weight based on the hydrocarbon.

6. A process according to claim 4 in which the amount of 2-nitropropane is about 0.05 to 0.08% by weight based on the hydrocarbon.

International Encyclopedia of Pressurized Packaging (Aerosols), Pergamon Press, ed. by Herzka (1966), page 329.

JOHN D. WELSH, Primary Examiner U.S. Cl. X.R. 252-396, 305 

